1. Field of the Invention
The present invention relates to a liquid housing container, and in particular, to a liquid housing container comprising a liquid supply connection portion.
2. Description of the Related Art
Liquid containers used in ink jet printing apparatuses may be integrated with or separated from print elements. A liquid container integrated with a print element can be easily replaced with a new one. Further, every time the container with ink used up is replaced with a new one, the print element is also replaced with a new one. Every time a print element has been used for a specified time, printing can be performed with a new print element.
On the other hand, for a liquid container separated from a print element, only the container needs to be replaced. This advantageously reduces the costs of replacement parts. However, the liquid container separated from the print element requires a liquid connection portion through which the print element is supplied with ink.
As a method for liquid connection, various systems have been adopted for ink jet printing apparatuses.
An example of a liquid container containing an ink absorbent with a capillary force in order to impregnate the ink absorbent with ink is a liquid container including an ink guiding member made of a bundle of fibers as disclosed in Japanese Patent Publication No. 2727292. Liquid connection based on the pressure contact of the ink guiding member with a filter in a printing apparatus is commonly adopted. This system advantageously uses a simple structure and allows the ink in the ink absorbent to be reliably consumed. However, ink jet printing apparatuses have been desired to exhibit improved filtering performance in order to deal with finer droplets ejected therefrom. Further, there has been a demand for an increase in the amount of ink flowing in per unit time during ink supply in order to reduce printing time. An increase in the amount of inflow ink is likely to increase the impact of possible pressure loss in a filter portion during ink supply. Measures such as an increase in the area of the filter have thus been required to prevent the possible pressure loss. However, this in turn requires a large opening, possibly causing the surroundings to be stained with ink during operation.
In contrast, to avoid the surface contact between the liquid container and the printing apparatus, a connection system based on a needle and a rubber plug has been proposed. Japanese Patent Publication No. 2519871 discloses a liquid container using a rubber plug. Liquid connection is established by sticking, into a rubber plug in a liquid container, a needle which is hollow and which has a sharp tip and a hole normally formed in its side surface and serving as a liquid channel. FIG. 29 of Japanese Patent Laid-Open No. 10-128992 and FIG. 7 of Japanese Patent Laid-Open No. 10-235892 disclose a configuration in which a rubber plug with a hole already formed therein is assembled in a liquid container. This configuration enables the printing apparatus and the liquid container to be connected together even if the needle does not have a sharp tip. These systems allow the connection function to be achieved by the simple structure.
However, these systems use only the restoring force of the rubber plug to prevent leakage of ink when the liquid connection is canceled. After the connection between the rubber plug and the needle is maintained for a long period, the hole in the rubber plug may not be completely closed during non-connection, depending on the material characteristics of the rubber plug or the diameter of the needle stuck into the rubber plug.
As a structure closing the hole during non-connection, a known system closes a hole formed in a rubber plug using a valve biased by a spring as disclosed in Japanese Patent Publication No. 2866068.
FIGS. 14A to 14C are cross-sectional views showing the configuration of a liquid container based on a system of closing a hole by means of a spring. Reference character R denotes an internal chamber in the liquid container. Reference numerals 902, 903, and 904 denote a valve, a spring, and a spring receiver, respectively. Reference numerals 906 and 907 denote an elastic body and a supply needle, respectively.
FIG. 14A is a diagram showing the internal structure of a supply connection portion of the liquid container. In the liquid container shown in FIG. 14A, the supply needle 907 is hollow and has a flat tip and a hole 907A in its side surface which serves as a liquid channel. The supply needle 907 shown by an alternate long and two short dashes line is moved to a position shown by a solid line to push the valve 902 shown by an alternate long and two short dashes line into the position of the valve 902 shown by a solid line, that is, into the internal chamber R in the liquid container. This results in the formation of a liquid channel.
FIG. 14B shows a connection portion valve structure of an ink housing bag (liquid container) disclosed in Japanese Patent Laid-Open No. 2005-199516. In a liquid container shown in FIG. 14B, the supply needle 907 has a sharp tip and a plurality of small-diameter holes 907B around the tip. The supply needle 907 shown by an alternate long and two short dashes line is moved to a position shown by a solid line to push the valve 902 shown by an alternate long and two short dashes line into the position of the valve 902 shown by a solid line, that is, into the internal chamber R in the liquid container. This results in the formation of a liquid channel.
FIG. 14C shows an example in which liquid connection is established using the gap between the supply needle and the valve; this configuration is disclosed in Japanese Patent Laid-Open No. 2005-193636 and U.S. Patent Publication No. 20040183870. In a liquid container shown in FIG. 14C, the supply needle 907 has an open tip and a recessed and projecting portion 907C in a circumferential portion of the tip. The supply needle shown by an alternate long and two short dashes line is moved to a position shown by a solid line to push the valve 902 shown by an alternate long and two short dashes line into the position of the valve 902 shown by a solid line, that is, into the internal chamber R in the liquid container. This results in the formation of a liquid channel through the gap between the valve 902 and the supply needle 907.
In these structures, the needle and the valve are in contact with each other to prevent a filter from being exposed to a liquid connection portion. Thus, the structure of the connection portion does not depend on the filter area. This makes the connection portion unlikely to be stained in spite of possible malfunction, while ensuring the appropriate filter area.
Japanese Patent Laid-Open No. 2006-043922 discloses a configuration in which the connection between the liquid housing container and the printing apparatus is such that the connection portion except for an ink supply portion is not closed. Specifically, in the ink supply portion, the liquid housing container and the printing apparatus (tank holder) are connected together via a closing seal portion. In the connection portion except for the ink supply portion, the liquid housing container and the printing apparatus are connected together using an alternate mechanism provided on a side surface of the liquid housing container.
FIG. 15 shows an example of an ink jet printing apparatus using a connection method disclosed in FIGS. 14A to 14C. Reference numeral 900 denotes an ink jet printing apparatus main body, and reference numeral 901 denotes a liquid container. In this ink jet printing apparatus, a print element (not shown) scans a print medium to print the surface of the print medium P. In connection with the print element, the liquid container 901 is installed at a specified position of the printing apparatus main body 900. In FIG. 15, four liquid containers 901 are installed on a front surface of the printing apparatus main body 900.
FIG. 16 is a diagram showing an example of the liquid container 901. Reference numeral 908 denotes a liquid supply portion. In this example, the liquid container 901 is shaped like a box. The liquid supply portion 908 is provided on an end surface of the liquid container 901 located in an installation direction (the direction of an arrow). The liquid container normally comprises a rubber plug or a valve as described above which is joined to a supply needle provided in the printing apparatus main body,
In recent years, the printing speed of ink jet printing apparatuses has been further increased. For the system based on the connection of the supply needle, reducing pressure loss has become important because of an increase in the amount of ink supplied per unit time. Moreover, the number of ink types has been increasing. For example, pigment ink tends to be more viscous than conventional dye ink, contributing to further increasing pressure loss.
Further, some ink jet printing apparatuses do not supply ink from ink tanks during printing but during non-printing. Since no ink is supplied during printing, the pressure on the ink supplied to the print element is unlikely to vary. This prevents ink ejection from being affected by a possible variation in ink pressure, allowing accurate ejection.
However, when the ink from the ink tank is not supplied during printing but during non-printing, the supply of a sufficient amount of ink for printing needs to be completed in a short time because ink supply is performed only during non-printing. This is because the time for non-printing needs to be reduced in keeping with increasing printing speed of ink jet printing apparatuses. When the ink is supplied only during non-printing, a sufficient amount of ink needs to be supplied in a short time, so that the ink fed from the ink tank often flows faster than when the ink is always supplied. In this case, the pressure variation per unit time associated with ink supply increases, resulting in increased pressure loss.
To reduce the pressure loss, it is important to maximize the cross section of a channel through which ink passes. However, if a side hole is present in a side of the tip of a hollow needle as in the case of the liquid container disclosed in Japanese Patent Laid-Open No. 10-235892, it is difficult in connection with a manufacturing process to increase the diameter of the side hole; the size of the side hole is limited.
Further, in the liquid container shown in FIG. 14C, since the tip of the supply needle 907 abuts against the valve member 902, a recessed gap in the tip 907C of the supply needle 907 constitutes an ink channel. In this liquid container, the ink channel can be widened by increasing the width or depth of the recessed shape in the tip 907C of the supply needle 907. However, to fulfill the function of abutting the valve 902 against the needle, it is necessary to ensure the area in which the valve 902 abuts against the needle. This prevents the ink channel from being easily widened. Further, to reduce the ink pressure loss associated with the supply needle 907 itself, the inner diameter of the needle needs to be increased. However, an increase in the outer diameter of the needle in the connection portion may affect the closability during connection as well as installing operability. Moreover, an increase in the inner diameter and a reduction in the thickness of the supply needle 907 with its outer diameter unchanged make it difficult to increase the depth of the recess in the tip 907C of the supply needle 907 owing to the need to maintain the rigidity of the needle.
For the liquid container shown in FIG. 14B, in the conventional example, the supply needle 907 is made by molding resin. In this case, ink passes through the thin hole 908B, and the pressure loss in this portion needs to be reduced. However, the intervals of the holes 907B, through which the ink passes, depend on the fluidity of the resin and the strength of a mold during molding. This makes it difficult to reduce the intervals of the holes 907B to increase the number of holes 907B formed or to increase the inner diameter of the holes 907B.